Non-Patent Document 1 discloses that a homologous series represented by In1−xGa1+xO3(ZnO)m (−1≤x≤ and m is a natural number) exists. Furthermore, Non-Patent Document 1 discloses a solid solution range of a homologous series. For example, in the case of a solid solution range of a homologous series when m is 1, x is within a range from −0.33 to 0.08, and in the case of a solid solution range of a homologous series when m is 2, x is within a range from −0.68 to 0.32.
Furthermore, a technique in which a transistor is fabricated using an In—Ga—Zn-based oxide semiconductor is disclosed (for example, see Patent Document 1).